In pursuit of higher engine efficiencies, higher turbine inlet temperatures have been relied upon to boost overall engine performance. This can result in gas path temperatures that may exceed melting points of turbine component constituent materials. To address this issue, dedicated cooling air is extracted from a compressor section and is used to cool the gas path components in the turbine, such as rotating blades and stator vanes for example, incurring significant cycle penalties.
One method of cooling turbine airfoils utilizes internal cooling channels or cavities formed in the airfoil to promote convective heat transfer. Cooling air is typically routed from a root of the airfoil toward a tip. The cooling air is then discharged out of the airfoil through a plurality of holes formed along a length of the airfoil. The cooling air exiting the holes forms a film of cooler air that shields the airfoil from incoming combustion gases.
Typically, these cooling holes and significant cooling mass flow rates are required to provide the needed amount of cooling. In order to effectively cool the airfoils to protect against damage, there is a need to balance the amount of cooling flow used and the overall heat transfer capability.